Electrolyte Disorders and Arrhythmogenesis
Cardiology Journal 2011, Vol. 18, No. 3, pp. 233–245 Copyright © 2011 Via Medica REVIEW ARTICLE ISSN 1897–5593 Electrolyte disorders and arrhythmogenesis Nabil El-Sherif1, Gioia Turitto2 1State University of NY, Downstate Medical Center and NY Harbor VA Healthcare System, Brooklyn, NY, USA 2Methodist University Hospital, Brooklyn, NY, USA Abstract Electrolyte disorders can alter cardiac ionic currents kinetics and depending on the changes can promote proarrhythmic or antiarrhythmic effects. The present report reviews the mecha- nisms, electrophysiolgical (EP), electrocardiographic (ECG), and clinical consequences of elec- trolyte disorders. Potassium (K+) is the most abundent intracellular cation and hypokalemia is the most commont electrolyte abnormality encountered in clinical practice. The most signifcant ECG manifestation of hypokalemia is a prominent U wave. Several cardiac and + non cardiac drugs are known to suppress the HERG K channel and hence the IK, and especially in the presence of hypokalemia, can result in prolonged action potential duration and QT interval, QTU alternans, early afterdepolarizations, and torsade de pointes ventricu- lar tachyarrythmia (TdP VT). Hyperkalemia affects up to 8% of hospitalized patients mainly in the setting of compromised renal function. The ECG manifestation of hyperkalemia de- pends on serum K+ level. At 5.5–7.0 mmol/L K+, tall peaked, narrow-based T waves are seen. At > 10.0 mmol/L K+, sinus arrest, marked intraventricular conduction delay, ventricular techycardia, and ventricular fibrillation can develop. Isolated abnormalities of extracellular calcium (Ca++) produce clinically significant EP effects only when they are extreme in either direction. Hypocalcemia, frequently seen in the setting of chronic renal insufficiency, results in prolonged ST segment and QT interval while hypercalcemia, usually seen with hyperparathy- roidism, results in shortening of both intervals.
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